437 research outputs found
The European Flood Alert System â Part 1: Concept and development
International audienceThis paper presents the development of the European Flood Alert System (EFAS), which aims at increasing preparedness for floods in trans-national European river basins by providing local water authorities with medium-range and probabilistic flood forecasting information 3 to 10 days in advance. The EFAS research project started in 2003 with the development of a prototype at the European Commission Joint Research Centre (JRC), in close collaboration with the national hydrological and meteorological services. The prototype covers the whole of Europe on a 5 km grid. In parallel, different high-resolution data sets have been collected for the Elbe and Danube river basins, allowing the potential of the system under optimum conditions and on a higher resolution, to be assessed. Flood warning lead-times of 3â10 days are achieved through the incorporation of medium-range weather forecasts from the Deutscher Wetterdienst (DWD) and the European Centre for Medium-Range Weather Forecasts (ECMWF), comprising a full set of 51 probabilistic forecasts from the Ensemble Prediction System (EPS) provided by ECMWF. The ensemble of different hydrographs is analysed and combined to produce early flood warning information, which is disseminated to the hydrological services that have agreed to participate in the development of the system. In Part 1 of this paper, the scientific approach adopted in development of the system is presented. The rational of the project, the system's set-up, its underlying components, basic principles, and products, are described. In Part 2, results of a detailed statistical analysis of the performance of the system are shown, with regard to both probabilistic and deterministic forecast
The european flood alert system EFAS â Part 2: Statistical skill assessment of probabilistic and deterministic operational forecasts
Since 2005 the European Flood Alert System (EFAS) has been producing probabilistic hydrological forecasts in pre-operational mode at the Joint Research Centre (JRC) of the European Commission. EFAS aims at increasing preparedness for floods in trans-national European river basins by providing medium-range deterministic and probabilistic flood forecasting information, from 3 to 10 days in advance, to national hydro-meteorological services. <br><br> This paper is Part 2 of a study presenting the development and skill assessment of EFAS. In Part 1, the scientific approach adopted in the development of the system has been presented, as well as its basic principles and forecast products. In the present article, two years of existing operational EFAS forecasts are statistically assessed and the skill of EFAS forecasts is analysed with several skill scores. The analysis is based on the comparison of threshold exceedances between proxy-observed and forecasted discharges. Skill is assessed both with and without taking into account the persistence of the forecasted signal during consecutive forecasts. <br><br> Skill assessment approaches are mostly adopted from meteorology and the analysis also compares probabilistic and deterministic aspects of EFAS. Furthermore, the utility of different skill scores is discussed and their strengths and shortcomings illustrated. The analysis shows the benefit of incorporating past forecasts in the probability analysis, for medium-range forecasts, which effectively increases the skill of the forecasts
The monetary benefit of early flood warnings in Europe
Effective disaster risk management relies on science-based solutions to close the gap between prevention and preparedness measures. The consultation on the United Nations post-2015 framework for disaster risk reduction highlights the need for cross-border early warning systems to strengthen the preparedness phases of disaster risk management, in order to save lives and property and reduce the overall impact of severe events. Continental and global scale flood forecasting systems provide vital early flood warning information to national and international civil protection authorities, who can use this information to make decisions on how to prepare for upcoming floods. Here the potential monetary benefits of early flood warnings are estimated based on the forecasts of the continental-scale European Flood Awareness System (EFAS) using existing flood damage cost information and calculations of potential avoided flood damages. The benefits are of the order of 400 Euro for every 1 Euro invested. A sensitivity analysis is performed in order to test the uncertainty in the method and develop an envelope of potential monetary benefits of EFAS warnings. The results provide clear evidence that there is likely a substantial monetary benefit in this cross-border continental-scale flood early warning system. This supports the wider drive to implement early warning systems at the continental or global scale to improve our resilience to natural hazards
Optimization of the Fading MIMO Broadcast Channel: Capacity and Fairness Perspectives
Multiple input multiple output (MIMO) systems are now a proven area in
current and future telecommunications research. MIMO wireless channels, in
which both the transmitter and receiver have multiple antennas, have been
shown to provide high bandwidth efficiency. In this thesis, we cover MIMO
communications technology with a focus on cellular systems and the MIMO
broadcast channel (MIMO-BC).
Our development of techniques and analysis for the MIMO-BC starts with
a study of single user MIMO systems. One such single user technique is that of
antenna selection. In this thesis, we discuss various flavours of antenna selection, with the focus on powerful, yet straightforward, norm-based algorithms.
These algorithms are analyzed and the results of this analysis produce a powerful and flexible power scaling factor. This power scaling factor can be used
to model the gains of norm-based antenna selection via a single signal-to-noise
ratio (SNR)-based parameter. This provides a powerful tool for engineers interested in quickly seeing the effects of antenna selection on their systems. A
novel low complexity power allocation scheme follows on from the selection
algorithms. Named âPoor Manâs Waterfillingâ (PMWF), this scheme can provide significant gains in low SNR systems with very little extra complexity
compared to selection alone.
We then compare a variety of algorithms for the MIMO-BC, ranging from
selection to beamforming, to the optimal, yet complex, iterative waterfilling
(ITWF) solution. In this thesis we show that certain algorithms perform better
in different scenarios, based on whether there is shadow fading or not. A power
scaling factor analysis is also performed on these systems. In the cases where
the userâs link gains are widely varying, such as when shadowing and distance
effects are present, user fairness is impaired when optimal and near optimal
throughput occurs.
This leads to a key problem in the MIMO-BC, the balance between user
fairness and throughput performance. In an attempt to find a suitable balance
between these two factors, we modify the ITWF algorithm by both introducing extra constraints and also by using a novel utility function approach. Both
these methods prove to increase user fairness with only minor loss in throughput over the optimal systems.
The introduction of MIMO systems to the cellular domain has been hampered by the effects of interference between the cells. In this thesis we move
MIMO to the cellular domain, addressing the interference using two different
methods. We first use power control, where the transmit power of the base
station is controlled to optimize the overall system throughput. This leads
to promising results using low complexity methods. Our second method is a
novel method of collaboration between base stations. This collaboration transforms neighbouring cell sectors into macro-cells and this results in substantial
increases in performance
The European Flood Alert System - Part 1: Concept and Development
This paper presents the development of the European Flood Alert System (EFAS), which aims at increasing preparedness for floods in trans-national European river basins by providing local water authorities with medium-range and probabilistic flood forecasting information 3 to 10 days in advance.
The EFAS research project started in 2003 with the development of a prototype at the European Commission Joint Research Centre (JRC), in close collaboration with the national hydrological and meteorological services. The prototype covers the whole of Europe on a 5 km grid. In parallel, different high-resolution data sets have been collected for the Elbe and Danube river basins, allowing the potential of the system under optimum conditions and on a higher resolution, to be assessed.
Flood warning lead-times of 3-10 days are achieved through the incorporation of medium-range weather forecasts from the Deutscher Wetterdienst (DWD) and the European Centre for Medium-Range Weather Forecasts (ECMWF), comprising a full set of 51 probabilistic forecasts from the Ensemble Prediction System (EPS) provided by ECMWF. The ensemble of different hydrographs is analysed and combined to produce early flood warning information, which is disseminated to the hydrological services that have agreed to participate in the development of the system.
In Part I of this paper, the scientific approach adopted in development of the system is presented. The rational of the project, the systemÂżs set-up, its underlying components, basic principles, and products, are described. In Part II, results of a detailed statistical analysis of the performance of the system are shown, with regard to both probabilistic and deterministic forecastsJRC.H.7-Land management and natural hazard
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Forecast convergence score: a forecaster's approach to analysing hydro-meteorological forecast systems.
In this paper the properties of a hydro-meteorological forecasting system for forecasting river flows have been analysed using a probabilistic forecast convergence score (FCS). The focus on fixed event forecasts provides a forecaster's approach to system behaviour and adds an important perspective to the suite of forecast verification tools commonly used in this field. A low FCS indicates a more consistent forecast. It can be demonstrated that the FCS annual maximum decreases over the last 10 years. With lead time, the FCS of the ensemble forecast decreases whereas the control and high resolution forecast increase. The FCS is influenced by the lead time, threshold and catchment size and location. It indicates that one should use seasonality based decision rules to issue flood warnings
Yolk sac tumor of the ovary
Background: A 10-year-old girl presented to the emergency department with acute abdominal pain in the right fossa. There was no known previous medical history. She had a fever up to 38,4°C without any complaints of nausea, vomiting or diarrhea
T Cells Contain an RNase-Insensitive Inhibitor of APOBEC3G Deaminase Activity
The deoxycytidine deaminase APOBEC3G (A3G) is expressed in human T cells and inhibits HIV-1 replication. When transfected into A3G-deficient epithelial cell lines, A3G induces catastrophic hypermutation by deaminating the HIV-1 genome. Interestingly, studies suggest that endogenous A3G in T cells induces less hypermutation than would be expected. However, to date, the specific deaminase activity of endogenous A3G in human CD4+ T cells has not been examined directly. Here, we compared deaminase activity of endogenous and exogenous A3G in various human cell lines using a standard assay and a novel, quantitative, high-throughput assay. Exogenous A3G in epithelial cell lysates displayed deaminase activity only following RNase treatment, as expected given that A3G is known to form an enzymatically inactive RNA-containing complex. Surprisingly, comparable amounts of endogenous A3G from T cell lines or from resting or activated primary CD4+ T cells exhibited minimal deaminase activity, despite RNase treatment. Specific deaminase activity of endogenous A3G in H9, CEM, and other T cell lines was up to 36-fold lower than specific activity of exogenous A3G in epithelial-derived cell lines. Furthermore, RNase-treated T cell lysates conferred a dose-dependent inhibition to epithelial cell lysates expressing enzymatically active A3G. These studies suggest that T cells, unlike epithelial-derived cell lines, express an unidentified RNase-resistant factor that inhibits A3G deaminase activity. This factor could be responsible for reduced levels of hypermutation in T cells, and its identification and blockade could offer a means for increasing antiretroviral intrinsic immunity of T cells
Flemish Normative Data for the Buschke Selective Reminding Test
The purpose of this study was to provide normative data for a Flemish version of the Buschke Selective Reminding Test (SRT). The SRT allows for the simultaneous analysis of several components of verbal memory, such as short and long term retrieval. The Flemish SRT was administered to 3257 neurologically healthy adults (1627 men and 1630 women, age range = 18â94 years). Effects of age, sex and education on SRT performance were assessed. Results indicate that SRT performance decreased with age and that this decline accelerated in men compared to women. Furthermore, an effect of education was found favoring participants who completed a higher education. Normative data quantified through percentile ranks and stratified by age, sex and education level are provided
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